This Theme Issue exemplifies the significant progress that has been made in our understanding of the formation and nature of molecular assemblies, and the consequent construction of functional nanostructures. The diversity of nanostructures derived from molecular assemblies is a manifestation of a convergence of research interests in the physical, chemical, material and biological sciences. The discussions of the characteristics of the various molecular assemblies presented in this Theme Issue reflect the diverse nature of the interactions between the various building blocks; this versatility leads to a wide variety of molecular nanomaterials which have a broad range of technological applications.

Molecular assembly is generally considered to be an ideal strategy when seeking to construct a functional nanostructure via a ‘bottom-up’ approach as this allows the incorporation of a rich variety of designed building blocks. The outcome of the molecular self-assembly process depends upon a variety of factors including: the nature of the functional groups present on the assembling molecules, the temperature at which the molecules assemble, the environment in which the process occurs (e.g. ultra-high vacuum or solution) and the concentration of the building blocks (Mali & De Feyter [1], Yan et al. [2]). Therefore, each of these parameters can have a significant influence on the nature of the nanomaterial produced and be critical for the extent of its practical utility owing to, for example, its magnetic (Wang et al. [3]) or optical (Liu et al. [4]) properties.

The intrinsic diversity in the chemical functionality of building blocks requires an understanding of the principles of assembly at all levels, that is, from the molecules to the nanoparticles and beyond. Complementary interactions between building blocks are the major factors in determining the stability of a molecular assembly and are the key to understanding the nature of a phase-separated molecular assembly, the heterogeneity of structures in a multi-component assembly and the influence of the environment on the kinetics of product formation. A variety of intermolecular interactions, such as hydrogen bonding, van der Waals forces, covalent and coordinate bonds, have been used successfully in the designed assembly of polymeric architectures (Xu et al. [5]). Hydrogen bonding has the advantages of selectivity and directionality, and is an important interaction in many systems, e.g. those containing carboxylate groups, whereas van der Waals forces are the dominant interactions in the molecular interactions of molecules that involve a long linear alkane chain (Yan et al. [2]). These interactions are faithfully reflected in the structural analysis of peptide assemblies relating to various degenerative diseases (Yang & Wang [6]).

The potential applications of molecular nanostructures are manifold and, as illustrated in this Theme Issue, increasing rapidly. Block copolymers are showing considerable promise in photolithographic approaches to the generation of semiconductor devices that may lead to advances in computing power beyond those predicted by Moore's law (Gu et al. [7]). Another promising application can be observed in the development of high efficacy drug delivery systems derived from controlled-release drugs encapsulated in polymeric micelles (Wang et al. [8]). Also, RNA nanotechnology has emerged as a new field with the production of nanoparticles which show considerable promise in molecular-scale computing (Qiu et al. [9]). Microporous organic frameworks can possess a large internal surface area yet exhibit a high stability; some of these materials bind greenhouse gases from dry air (Pei et al. [10]) and others have been used as the host of a dye in the photoanode of a solar cell (Liu et al. [11]). With an amazingly rich variety of molecularly decorated nano/micro structures, the exploratory efforts in various environmental and chemical processes can be very rewarding (Zhao et al. [12]). Further examples of the potential applications of molecular self-assembly in nanotechnology have arisen in the field of plastic electronics including the construction of nanowires, field-effect transistors, photodetectors and optical waveguides (Xie et al. [13]). The incorporation with novel nanostructures such as conducting graphene (Zhu et al. [14]) in sensory structures (Wang et al. [15]) is key for developing novel devices based on molecular nanotechnology.

Thus, this dynamic field of interdisciplinary science is experiencing major developments and generating an exciting range of novel materials, many of which have exciting possible application implications. The dedicated efforts reflected in this Theme Issue also indicate a number of genuine challenges towards tangible technological impacts. The fundamental insights of molecular nanotechnology for overcoming the limiting factors, such as control of assembly kinetics, stability of assembly architectures, availability of materials suitable for assembly processes, etc., will be key for shaping the future trends in this field. We are confident that, for the foreseeable future, the advances achieved in the control of molecular assembly will continue, thereby generating new and strategically important applications of the resultant nanotechnology.

Acknowledgements

We are grateful for the communications with Prof. Dave Garner that led to the production of this Theme Issue. Also, we sincerely thank Prof. Steven De Feyter and Thomas Russell and all of our Chinese colleagues for their valuable contributions to, and creative scientific perspectives of, molecular nanostructures and nanotechnology presented in this Theme Issue.